Rubber composition and tire using the same

ABSTRACT

This invention relates to a rubber composition possessing high wear resistance and low heat buildup, and more particularly to a rubber composition comprising 100 parts by mass of a diene polymer and 20-250 parts by mass of a carbon black as a filler, characterized in that the carbon black has a dibutyl phthalate (DBP) absorption number of 40-180 cm 3 /100 g, a nitrogen adsorption specific surface area (N 2 SA) of 40-300 m 2 /g, a tint strength (TINT) of 50-150% and a light transmittance of toluene extract of not less than 90% and a relation between the nitrogen adsorption specific surface area and the light transmittance of toluene extract satisfies the following equation (I): 
 
0.0283× A ×(100− B )≦40  (I) 
(wherein A is a nitrogen adsorption specific surface area and B is a light transmittance of toluene extract).

excellent wear resistance and low heat buildup in which the above rubber composition is applied to a tread.

The inventors have made various studies for achieving the above objects and found that when a diene polymer is compounded with a carbon black to form a rubber composition, the diene polymer is highly reinforced by using a carbon black being less in a tar component existing on its surface, particularly polycyclic aromatic component, whereby high fracture strength and wear resistance are obtained in the rubber composition and further heat buildup of the rubber composition is suppressed to a low level, and as a result, the invention has been accomplished.

That is, the rubber composition according to the invention is a rubber composition comprising 100 parts by mass of a diene polymer and 20-250 parts by mass of a carbon black as a filler, characterized in that the carbon black has a dibutyl phthalate (DBP) absorption number of 40-180 cm³/100 g, a nitrogen adsorption specific surface area (N₂SA) of 40-300 m²/g, a tint strength (TINT) of 50-150% and a light transmittance of toluene extract of not less than 90% and a relation between the nitrogen adsorption specific surface area and the light transmittance of toluene extract satisfies the following equation (I): 0.0283×A×(100−B)≦4  (I) (wherein A is a nitrogen adsorption specific surface area and B is a light transmittance of toluene extract).

In a preferable embodiment of the rubber composition according to the invention, the relation between the nitrogen adsorption specific surface area and the light transmittance of toluene extract satisfies the following equation (II): 0.0283×A×(100−B)≦20  (II) (wherein A and B are the same as mentioned above).

At this moment, it is further preferable that the relation between the nitrogen adsorption specific surface area and the light transmittance of toluene extract satisfies the following equation (III): 0.0283×A×(100−B)≦8  (III) (wherein A and B are the same as mentioned above).

In another preferable embodiment of the rubber composition according to the invention, the carbon black has a maximum ultraviolet (UV) absorbance at 330-340 nm of not more than 0.020 and a maximum ultraviolet (UV) absorbance at 260-280 nm of not more than 0.020.

In the other preferable embodiment of the rubber composition according to the invention, the carbon black has a weight reduction ratio at 400-530° C. of not more than 0.20%.

In a further preferable embodiment of the rubber composition according to the invention, the carbon black has an extraction ratio with dichloromethane of not more than 0.12%.

In a still further preferable embodiment of the rubber composition according to the invention, the carbon black has a hydrogen emitting ratio at 2000° C. of not less than 0.15%. At this moment, the carbon black is preferable to have a hydrogen emitting ratio at 2000° C. of not less than 0.18%, more preferably not less than 0.23%.

Further, the tire according to the invention is characterized by using the above rubber composition in a tread.

BEST MODE FOR CARRYING OUT THE INVENTION

The invention will be described in detail below. The rubber composition according to the invention comprises 20-250 parts by mass of a carbon black as a filler based on 100 parts by mass of a diene polymer, in which the carbon black has a dibutyl phthalate (DBP) absorption number of 40-180 cm³/100 g, a nitrogen adsorption specific surface area (N₂SA) of 40-300 m²/g, a tint strength (TINT) of 50-150% and a light transmittance of toluene extract of not less than 90% and a relation between the nitrogen adsorption specific surface area and the light transmittance of toluene extract satisfies the above equation (I). In this carbon black, the DBP absorption number, N₂SA and TINT satisfy the above ranges and the light transmittance of toluene extract is not less than 90%, so that the tar component existing on the surface is sufficiently small and the composite between the carbon black and the rubber component is efficiently caused, whereby the wear resistance of the rubber composition can be considerably improved, and at the same time, the heat buildup of the rubber composition can be lowered.

The carbon black used in the rubber composition according to the invention is preferable to have a dibutyl phthalate (DBP) absorption number of 40-180 cm³/100 g, preferably 70-170 cm³/100 g. When the DBP absorption number of the carbon black is less than 40 cm³/100 g, the minimum tensile stress required as a rubber composition for the tire can not be developed, while when it exceeds 180 cm³/100 g, a minimum elongation required can not be ensured.

The carbon black used in the rubber composition according to the invention has a nitrogen adsorption specific surface area (N₂SA) of 40-300 m²/g, preferably 70-250 m²/g, more preferably 70-170 m²/g. When the nitrogen adsorption specific surface area of the carbon black is less than 40 m²/g, the minimum strength (tensile strength) required as a rubber composition for the tire can not be developed, while when it exceeds 300 m²/g, the dispersibility in the rubber composition can not be sufficiently ensured and hence the wear resistance and the like of the rubber composition are deteriorated.

The carbon black used in the rubber composition according to the invention has a tint strength (TINT) of 50-150%, preferably 90-145%. When the tint strength of the carbon black is less than 50%, the strength and wear resistance durable in the tire when the rubber composition is applied to the tread can not be developed, while when it exceeds 150%, the viscosity of rubber remarkably rises and it is difficult to provide the rubber composition.

The carbon black used in the rubber composition according to the invention has a light transmittance of toluene extract of not less than 90%, preferably not less than 95%. When the light transmittance of toluene extract in the carbon black is less than 90%, the tar component existing on the surface of the carbon black, particularly aromatic component becomes large, and hence the rubber composition can not be sufficiently reinforced and the wear resistance and the like of the rubber composition lower.

As to the carbon black used in the rubber composition according to the invention, the nitrogen adsorption specific surface area and the light transmittance of toluene extract satisfy the relation of the equation (I), preferably the relation of the equation (II), more preferably the relation of the equation (III) as an absolute value. When a left side in the equations (I), (II) and (III) exceeds 40, the tar component becomes large on the surface of the carbon black, and hence the rubber composition can not be sufficiently reinforced and the wear resistance lowers.

The carbon black used in the rubber composition according to the invention is preferable to have a maximum ultraviolet (UV) absorbance at 330-340 nm of not more than 0.020 and a maximum ultraviolet (UV) absorbance at 260-280 nm of not more than 0.020. As the maximum UV absorbances at 330-340 nm and 260-280 nm become small, the aromatic component existing on the surface of the carbon black become less. Therefore, by using the carbon black having the maximum UV absorbances at 330-340 nm and 260-280 nm of not more than 0.020 can be given a high reinforcing property to the rubber composition to thereby improve the wear resistance and the like.

The carbon black used in the rubber composition according to the invention is preferable to have a weight reduction ratio at 400-530° C. of not more than 0.20%. As the weight reduction ratio at 400-530° C. becomes small, the aromatic component existing on the surface of the carbon black become less. Therefore, by using the carbon black having the weight reduction ratio at 400-530° C. of not more than 0.20% can be given a high reinforcing property to the rubber composition to thereby improve the wear resistance and the like.

The carbon black used in the rubber composition according to the invention is preferable to have an extraction ratio with dichloromethane of not more than 0.12%. As the extraction ratio with dichloromethane becomes small, the aromatic component existing on the surface of the carbon black become less. Therefore, by using the carbon black having the extraction ratio with dichloromethane of not more than 0.12% can be given a high reinforcing property to the rubber composition to thereby improve the wear resistance and the like.

As to the carbon black used in the rubber composition according to the invention, the hydrogen emitting ratio at 2000° C. is preferably not less than 0.15%, more preferably not less than 0.18%, particularly not less than 0.23%. At this moment, the hydrogen emitting ratio at 2000° C. means a ratio of hydrogen quantity produced when the carbon black is heated at 2000° C. for 15 minutes to the mass of the carbon black. When the carbon black having a hydrogen emitting ratio at 2000° C. of less than 0.15% is used in the rubber composition, the wear resistance of the rubber composition lowers, and the heat buildup of the rubber composition undesirably becomes large.

The rubber composition according to the invention contains 20-250 parts by mass of the carbon black as a filler based on 100 parts by mass of the diene polymer as a rubber component. When the amount of the carbon black is less than 20 parts by mass, the rigidity of the rubber is low and the wear resistance is insufficient, while when it exceeds 250 parts by mass, the rubber composition becomes too hard, and the wear resistance rather lowers and further the processability of the rubber composition is extremely deteriorated.

As the diene polymer used as a rubber component in the rubber composition according to the invention are mentioned natural rubber (NR), styrene-butadiene copolymer rubber (SBR), styrene-isoprene copolymer rubber (SIR), polyisoprene rubber (IR), poly-butadiene rubber (BR) and the like. They may be used alone or in a combination of two or more.

In addition to the above carbon black and the diene polymer, the rubber composition may be properly compounded with additives usually used in the rubber industry such as a filler other than carbon black, a vulcanizing agent, a vulcanization accelerator, an antioxidant, a scorch retarder, a softening agent, zinc oxide, stearic acid, a silane coupling agent and the like within a scope not damaging the object of the invention. As these additives can be preferably used commercially available ones. Moreover, the rubber composition can be produced by compounding the diene polymer with the carbon black and, if necessary, various additives properly selected, and milling them and warming up and extruding and the like.

The tire according to the invention is characterized by using the above rubber composition in the tread. Since the rubber composition is excellent in the wear resistance and low heat buildup, the tire according to the invention is excellent in the wear resistance and low fuel consumption.

The following examples are given in illustration of the invention and are not intended as limitations thereof.

EXAMPLES

(Production Method of Carbon Black)

In a furnace for the production of carbon black are produced carbon blacks having various properties by properly adjusting an air-introducing condition, a starting oil-introducing condition, and a position and an amount of water introduced for the stop of the reaction and a subsequent temperature, and if necessary, introducing a compound such as water, air or the like into the furnace at a subsequent step. Furthermore, the carbon blacks having various properties are obtained by properly adjusting a drying temperature (150-250° C.) of the carbon black after the granulation, if necessary.

With respect to the thus obtained carbon blacks, the dibutyl phthalate (DBP) absorption number according to ASTM D2414-88 (JIS K6217-97), nitrogen adsorption specific surface area (N₂SA) according to ASTM D3037-88, tint strength (TINT) according to ASTM D3265-88 and light transmittance of toluene extract according to JIS K6218-97 are measured, respectively, and further the UV absorbance, weight reduction ratio, extraction ratio with dichloromethane and hydrogen emitting ratio at 2000° C. are measured by the following methods. The results are shown in Tables 2 and 3.

(1) UV Absorbance

{circle around (1)} A carbon black sample is dried in an isothermal drier at 105° C. for 1 hour and cooled to room temperature in a desiccator.

{circle around (2)} 3.00 g of the sample is weight in an Erienmeyer flask of 100 mL with a co-plug.

{circle around (3)} To the flask is added 30 mL of cyclohexane, which is plugged and violently oscillated for 60 seconds and then left to stand at room temperature for 6 hours.

{circle around (4)} The mixed solution is filtered through a filtrating paper dried at 105° C., and a filtrate is placed into a quartz cell for the UV measurement.

{circle around (5)} A solution obtained by carrying out the above operations {circle around (3)}-{circle around (4)} without using the carbon black sample is placed into two quartz cells for the UV measurement, and one of these cells is set to a reference-side light path of a UV measuring device and the other is set to a sample-side light path, and they are adjusted (corrected) at 0-100%.

{circle around (6)} With respect to the filtrate obtained in the item {circle around (4)}, maximum light absorbance at 330-340 nm and 260-280 nm are measured.

(2) Weight Reduction Ratio

{circle around (1)} A carbon black sample is dried in an isothermal drier at 105° C. for 1 hour and cooled to room temperature in a desiccator.

{circle around (2)} About 10 mg of the sample is weighed on a metal pan for the TGA measurement and subjected to TGA (thermal weight analysis) under a stream of nitrogen gas.

{circle around (3)} The temperature of the sample is raised from 40° C. to 600° C. at a rate of 10° C./min to measure a weight reduction ratio from 400° C. to 530° C. based on the initial weight {circle around (2)}.

(3) Extraction Ratio with Dichloromethane

{circle around (1)} About 15 g of a carbon black sample is weighed and placed in a cylindrical filtering paper.

{circle around (2)} It is refluxed by heating in a Soxhlet extractor using dichloromethane as an extraction solvent for 30 hours.

{circle around (3)} The extract is dried through evaporation to measure a mass of the residue to thereby determine a mass percentage (ratio of component extracted with dichloromethane).

(4) Hydrogen Emitting Ratio at 2000° C.

{circle around (1)} A carbon black sample is dried in an isothermal drier at 105° C. for 1 hour and cooled to room temperature in a desiccator.

{circle around (2)} About 10 g of the sample is weighed in a tubular vessel made of tin, which is closed by pressing.

{circle around (3)} An amount of hydrogen produced when it is heated in a hydrogen analyzing device (EMGA621W, made by Horiba Seisakusho) at 2000° C. under a steam of argon gas for 15 minutes is measured to determine a mass percentage.

A rubber composition using the above carbon black according to a compounding recipe shown in Table 1 (amount of sulfur compounded is shown in Table 2) is milled in a Banbury mixer and further vulcanized in a pressure type vulcanizing apparatus at 145° C. for 30 minutes to obtain a vulcanized rubber. With respect to the resulting vulcanized rubber, the hardness according to JIS K6253-1997, the elongation at break, tensile strength and tensile stress at 300% elongation according to JIS K6251-1993 and the rebound resilience according to JIS K6255-1996 are measured, respectively, and further the wear resistance is evaluated by the following method. These results are shown in Tables 2 and 3. Moreover, the rebound resilience is represented by an index on the basis that the rebound resilience of a test specimen as a standard for comparison is 100, in which the larger the index value, the higher the rebound resilience and the better the low heat buildup.

(5) Wear Resistance of Vulcanized Rubber

A wear loss quantity is measured by using a Lambourn abrasion tester and then an index of wear resistance is calculated according to the following equation. Moreover, the larger the index value, the better the wear resistance.

Equation: index of wear resistance=wear loss quantity of a test specimen as a standard for comparison/wear loss quantity of each rubber test specimen×100

Furthermore, tires for truck and tires for passenger car are prepared by applying the rubber composition to a tread, and the wear resistance and heat buildup thereof are evaluated by the following methods. These results are shown in Tables 2 and 3.

(6) Wear Resistance of Tire

After the tire is mounted onto a truck or a passenger car and run over a distance of 20000 km for the passenger car tire or 4000 km for the truck tire, a residual amount of the groove, and the wear resistance is represented by an index on the basis that a reciprocate of the residual amount of the groove in the tire as a standard for the comparison is 100. The larger the index value, the better the wear resistance.

(7) Heat Buildup of Tire

After the tire is rotated on a steel drum under a constant load for a constant time, a temperature of a tire tread portion is measured, and the heat buildup is represented by an index on the basis that the a reciprocate of the temperature in the tread portion of the tire as a standard for the comparison is 100. The larger the index value, the better the low heat buildup. TABLE 1 For passenger car For truck Compounding NR (RSS#3) — 50 recipe of rubber cis-BR *1 — 50 composition SBR *2 100 — Carbon black 50 50 Aromatic oil *3 10 — Antioxidant 6PPD *4 1 1 Stearic acid 2 2 Zinc oxide 2.5 3 Vulcanization 0.6 0.8 accelerator BBS *5 Vulcanization 0.6 0.2 accelerator DPG *6 Vulcanization 0.6 — accelerator DM *7 Sulfur variable variable Tire size 185/60R14 11.0R22.5

In Table 1, *1 is BR01 made by JSR Corporation, *2 is #1500 made by JSR Corporation, *3 is AH-58 made by Idemitsu Kosan Co., Ltd., *4 is N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylene diamine, *5 is N-t-butyl-2-benzothiazole sulfenamide, *6 is diphenyl guanidine and *7 is dibenzothiazyl disulfide. TABLE 2 (a) Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Production Air total amount of air introduced (kg/h) 1490 1488 1493 1485 1490 1493 conditions introducing preheating temperature (° C.) 600 603 605 602 600 602 of carbon conditions amount of fuel introduced (kg/h) 75 74 75 73 75 75 black Raw oil amount introduced (kg/h) 355 352 357 365 355 354 introducing preheating temperature (° C.) 190 195 197 187 198 195 conditions Cooling residual time (milli second) 2.7 3.7 7.1 7.7 7.1 7.1 medium amount of cooling water (L/h) 291 295 289 427 305 304 introducing at first stage conditions amount of cooling water (L/h) 141 145 143 — — 130 at second stage Drying temperature of carbon black (° C.) 197 200 198 195 230 197 Properties DBP absorption number (cm³/100 g) 128 128 127 128 126 126 of carbon N₂SA (BET surface area) (m²/g) 131 131 130 130 132 132 black TINT (%) 132 132 132 132 133 133 Light transmittance of toluene extract (%) 99.2 98.8 99.1 99.2 96.1 95.8 0.0283 × A × (100 − B) — 3.0 4.4 3.3 2.9 14.6 15.7 UV absorbance (330-340 nm) (%) <0.001 <0.001 <0.001 0.001 0.005 0.030 UV absorbance (270-280 nm) (%) <0.001 <0.001 0.001 0.002 0.006 0.030 Weight reduction ratio (400-530° C.) (%) 0.01 0.01 0.01 0.01 0.11 0.11 Extraction ratio with dichloromethane (%) <0.01 <0.01 <0.01 <0.01 0.05 0.05 Hydrogen emitting ratio (2000° C.) (%) 0.25 0.22 0.16 0.14 0.17 0.17 Compounding recipe and tire size for truck Amount of sulfur compounded *2-1 (part by mass) 1.5 1.5 1.5 1.5 1.5 1.5 Properties Hardness — 67 67 66 67 67 67 of Elongation at break (%) 560 560 570 580 580 580 vulcanized Tensile strength (MPa) 31.0 30.8 30.4 30.0 29.1 28.8 rubber Tensile stress at 300% elongation (MPa) 14.4 14.2 14.1 13.7 14.7 14.5 Lambourn wear resistance (index) 128 122 117 108 113 109 Rebound resilience (index) 108 107 105 103 105 10.5 Evaluation Wear resistance of tire (index) 122 118 114 — — — Heart buildup of tire (index) 107 106 106 — — — (b) Example Example Example Example Example Example 7 8 9 10 11 12 Production Air total amount of air introduced (kg/h) 1495 1495 1500 1502 1500 1490 conditions introducing preheating temperature (° C.) 605 603 605 607 605 605 of carbon conditions amount of fuel introduced (kg/h) 75 75 77 77 77 75 black Raw oil amount introduced (kg/h) 360 350 363 362 360 345 introducing preheating temperature (° C.) 193 198 196 195 198 190 conditions Cooling residual time (milli second) 5.7 7.1 5.7 5.7 5.7 3.7 medium amount of cooling (L/h) 421 332 425 423 428 385 introducing water at first stage conditions amount of cooling (L/h) — 113 — — — 102 water at second stage Drying temperature of carbon black (° C.) 192 197 255 195 235 201 Properties DBP absorption number (cm³/100 g) 126 126 126 126 126 126 of carbon N₂SA (BET surface area) (m²/g) 132 132 132 132 132 129 black TINT (%) 133 133 133 133 133 130 Light transmittance of toluene extract (%) 95.5 93.2 93.5 92.7 92.8 90.5 0.0283 × A × (100 − B) — 16.8 25.4 24.3 27.3 26.9 34.7 UV absorbance (330-340 nm) (%) 0.005 0.011 0.010 0.015 0.016 0.016 UV absorbance (270-280 nm) (%) 0.005 0.012 0.012 0.016 0.017 0.017 Weight reduction ratio (400-530° C.) (%) 0.11 0.18 0.23 0.18 0.18 0.22 Extraction ratio with dichloromethane (%) 0.05 0.05 0.05 0.13 0.05 0.11 Hydrogen emitting ratio (2000° C.) (%) 0.13 0.16 0.16 0.16 0.17 0.23 Compounding recipe and tire size for truck Amount of sulfur compounded *2-1 (part by mass) 1.6 1.6 1.6 1.6 1.6 1.4 Properties Hardness — 67 67 67 67 67 68 of Elongation at break (%) 560 560 550 550 540 550 vulcanized Tensile strength (MPa) 28.6 29.0 28.6 28.5 28.0 29.1 rubber Tensile stress at 300% elongation (MPa) 14.6 14.8 14.8 14.8 14.8 14.8 Lambourn wear resistance (index) 106 111 105 106 109 110 Rebound resilience (index) 105 106 106 106 106 105 Evaluation Wear resistance of tire (index) — — — — — — Heart buildup of tire (index) — — — — — — *2-1 amount of sulfur compounded per 100 parts by mass of rubber component

TABLE 3 Compar- Compar- Compar- Compar- ative ative ative ative Example Example Example Example 1 2 3 4 Production Air total amount of air introduced (kg/h) 1490 1500 1510 1498 conditions introducing preheating temperature (° C.) 600 602 604 608 of carbon conditions amount of fuel introduced (kg/h) 75 77 78 75 black Raw oil amount introduced (kg/h) 355 352 350 345 introducing preheating temperature (° C.) 190 195 196 197 conditions Cooling residual time (milli second) 3.7 3.7 2.7 1.8 medium amount of cooling water at first stage (L/h) 496 498 502 498 introducing amount of cooling water at second stage (L/h) — — — — conditions Drying temperature of carbon black (° C.) 198 211 195 200 Properties DBP absorption number (cm³/100 g) 127 127 129 127 of carbon N₂SA (BET surface area) (m²/g) 129 130 132 130 black TINT (%) 132 133 132 132 Light transmittance of toluene extract (%) 88 86.9 65 40 0.0283 × A × (100 − B) — 43.8 51.5 130.7 220.7 UV absorbance (330-340 nm) (%) 0.080 0.130 0.180 0.220 UV absorbance (270-280 nm) (%) 0.100 0.140 0.190 0.250 Weight reduction ratio (400-530° C.) (%) 0.22 0.21 0.38 0.42 Extraction ratio with dichloromethane (%) 0.10 0.13 0.22 0.28 Hydrogen emitting ratio (2000° C.) (%) 0.17 0.17 0.22 0.28 Compounding recipe and tire size for truck Amount of sulfur compounded *3-1 (part by mass) 1.5 1.5 1.4 1.3 Properties Hardness — 66 64 67 67 of Elongation at break (%) 520 480 450 430 vulcanized Tensile strength (MPa) 26.2 25.6 22.9 21.2 rubber Tensile stress at 300% elongation (MPa) 14.4 13.8 14.7 14.6 Lambourn wear resistance (index) 101 100 90 79 Rebound resilience (index) 98 100 92 86 Evaluation Wear resistance of tire (index) — 100 — — Heart buildup of tire (index) — 100 — — Compar- Compar- ative ative Example Example Example Example 13 5 14 6 Production Air total amount of air introduced (kg/h) 1492 1488 1100 1150 conditions introducing preheating temperature (° C.) 603 602 598 597 of carbon conditions amount of fuel introduced (kg/h) 75 74 50 52 black Raw oil amount introduced (kg/h) 365 342 380 370 introducing preheating temperature (° C.) 196 198 185 187 conditions Cooling residual time (milli second) 4.7 0.77 78 41 medium amount of cooling water at first stage (L/h) 281 486 376 380 introducing amount of cooling water at second stage (L/h) 139 — — — conditions Drying temperature of carbon black (° C.) 195 201 202 205 Properties DBP absorption number (cm³/100 g) 125 126 114 112 of carbon N₂SA (BET surface area) (m²/g) 126 124 71 73 black TINT (%) 124 123 102 104 Light transmittance of toluene extract (%) 98 55 99 50 0.0283 × A × (100 − B) — 7.1 157.9 2.0 103.3 UV absorbance (330-340 nm) (%) 0.005 0.190 0.002 0.210 UV absorbance (270-280 nm) (%) 0.006 0.210 0.003 0.230 Weight reduction ratio (400-530° C.) (%) 0.05 0.32 0.08 0.34 Extraction ratio with dichloromethane (%) 0.10 0.22 0.11 0.25 Hydrogen emitting ratio (2000° C.) (%) 0.18 0.27 0.24 0.28 Compounding recipe and tire size for truck for passenger car Amount of sulfur compounded *3-1 (part by mass) 1.5 1.4 1.5 1.4 Properties Hardness — 63 62 58 57 of Elongation at break (%) 550 460 580 510 vulcanized Tensile strength (MPa) 29.1 27.0 23.2 20.8 rubber Tensile stress at 300% elongation (MPa) 13.6 13.2 12.1 12.1 Lambourn wear resistance (index) 114 100 116 100 Rebound resilience (index) 106 100 107 100 Evaluation Wear resistance of tire (index) 106 100 109 100 Heart buildup of tire (index) 105 100 107 100 *3-1 amount of sulfur compounded per 100 parts by mass of rubber

In Tables 2 and 3, Examples 1-12 and Comparative Examples 1, 3 and 4 are compared with the vulcanized rubber and tire of Comparative Example 2 as a standard, and Example 13 is compared with the vulcanized rubber and tire of Comparative Example 5 as a standard, and Example 14 is compared with the vulcanized rubber and tire of Comparative Example 6 as a standard.

As seen from Tables 2 and 3, the vulcanized rubbers of the examples are high in the Lambourn wear resistance and rebound resilience, and the tires using such rubber compositions are excellent in the wear resistance and low heat buildup. On the other hand, the vulcanized rubbers of the comparative examples compounded with the carbon black not satisfying the properties defined in the invention are low in the Lambourn wear resistance and rebound resilience as compared with the vulcanized rubbers of the examples, and the tires of the comparative examples using these rubber compositions are poor in the wear resistance and low heat buildup as compared with the tires of the examples.

INDUSTRIAL APPLICABILITY

According to the invention, by using a carbon black having particular properties and a small tar component in a rubber composition compounded with the carbon black can be provided a rubber composition having a high strength at break and excellent wear resistance and low heat buildup. Also, there can be provided a tire using such a rubber composition in a tread and having excellent wear resistance and low fuel consumption. 

1. A rubber composition comprising 100 parts by mass of a diene polymer and 20-250 parts by mass of a carbon black as a filler, characterized in that the carbon black has a dibutylphthalate (DBP) absorption number of 40-180 cm³/100 g, a nitrogen adsorption specific surface area (N₂SA) of 40-300 m²/g, a tint strength (TINT) of 50-150% and a light transmittance of toluene extract of not less than 90% and a relation between the nitrogen adsorption specific surface area and the light transmittance of toluene extract satisfies the following equation (I): 0.0283×A×(100−B)≦40  (I) (wherein A is a nitrogen adsorption specific surface area and B is a light transmittance of toluene extract).
 2. A rubber composition according to claim 1, wherein the relation between the nitrogen adsorption specific surface area and the light transmittance of toluene extract satisfies the following equation (II): 0.0283×A×(100−B)≦20  (II) (wherein A and B are the same as mentioned above).
 3. A rubber composition according to claim 2, wherein the relation between the nitrogen adsorption specific surface area and the light transmittance of toluene extract satisfies the following equation (III): 0.0283×A×(100−B)≦8  (III) (wherein A and B are the same as mentioned above).
 4. A rubber composition according to claim 1, wherein the carbon black has a maximum ultraviolet (UV) absorbance at 330-340 nm of not more than 0.020 and a maximum ultraviolet (UV) absorbance at 260-280 nm of not more than 0.020.
 5. A rubber composition according to claim 1, wherein the carbon black has a weight reduction ratio at 400-530° C. of not more than 0.20%.
 6. A rubber composition according to claim 1, wherein the carbon black has an extraction ratio with dichloromethane of not more than 0.12%.
 7. A rubber composition according to claim 1, wherein the carbon black has a hydrogen emitting ratio at 2000° C. of not less than 0.15%.
 8. A rubber composition according to claim 1, wherein the carbon black has a hydrogen emitting ratio at 2000° C. of not less than 0.18%.
 9. A rubber composition according to claim 1, wherein the carbon black has a hydrogen emitting ratio of not less than 0.23%.
 10. A tire characterized by using a rubber composition as claimed in claim 1 in a tread.
 11. A tire characterized by using a rubber composition as claimed in claim 2 in a tread.
 12. A tire characterized by using a rubber composition as claimed in claim 3 in a tread.
 13. A tire characterized by using a rubber composition as claimed in claim 4 in a tread.
 14. A tire characterized by using a rubber composition as claimed in claim 5 in a tread.
 15. A tire characterized by using a rubber composition as claimed in claim 6 in a tread.
 16. A tire characterized by using a rubber composition as claimed in claim 7 in a tread.
 17. A tire characterized by using a rubber composition as claimed in claim 8 in a tread.
 18. A tire characterized by using a rubber composition as claimed in claim 9 in a tread. 